1. Field of the Invention
The present invention relates to methods for preparing useful peptides, and more particularly to a solution synthesis method for preparing H-SAR-LYS-SAR-GLN-NH.sub.2 and compositions useful therein.
2. Description of the Prior Art
In U.S. patent application Ser. No. 960,550, filed Nov. 17, 1978, and entitled "New Tetrapeptides and Methods," a class of peptides is discloed as being useful in thymic function and immunological areas. One of the preferred members of this class has the formula H-SAR-LYS-SAR-GLN-NH.sub.2. This application is incorporated herein by reference. In the referenced application, the class of tetrapeptides was prepared by solid-phase synthesis techniques commonly described as "Merrifield Synthesis." It was also disclosed that classical techniques (i.e., solution synthetic techniques) may be employed to prepare this class of tetrapeptides. No specific classical method or synthetic route was disclosed.
While the solid-phase synthetic technique of Merrifield is a convenient one for preparation of small quantities of peptides in the laboratory, it would be impractical and generally uneconomic for preparation of large quantities (e.g., more than about 100 g) of peptide, for which solution synthesis techniques are more appropriate. Moreover, solution synthesis techniques are generally much less costly than solid phase techniques, due to the smaller amounts of reagents necessary and to the much lesser unit cost of certain of the reagents used. Among the large variety of solution synthetic techniques available for use in polypeptide preparations, Applicant has discovered a particular synthetic method which produces the desired tetrapeptide amide conveniently and economically.